/Engine/Plugins/Experimental/WaveFunctionCollapse/Source/WaveFunctionCollapse/Public/WaveFunctionCollapseSubsystem.h
Propagation phase: This process checks if the selection made during the observation is valid by checking constraint validity with neighboring tiles. Neighboring tiles may reduce their remaining options to include only valid options. If the remaining options of a tile were modified, the neighboring tiles of the modified tile will be added to a queue. During this process, if any contradiction (a tile with zero remaining options) is encountered, the current solve will fail.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="WFCFunctions") bool Propagate ( [TArray](API\Runtime\Core\Containers\TArray)< [FWaveFunctionCollapseTile](API\Plugins\WaveFunctionCollapse\FWaveFunctionCollapseTile) > & Tiles, [TArray](API\Runtime\Core\Containers\TArray)< int32 > & RemainingTiles, [TMap](API\Runtime\Core\Containers\TMap)< int32, [FWaveFunctionCollapseQueueElement](API\Plugins\WaveFunctionCollapse\FWaveFunctionCollapseQueueElemen-) > & ObservationQueue, int32 & PropagationCount )